The present invention relates to a child car seat having a back portion, in which an impact load at a time of impact can be absorbed by the back portion.
Generally, when a newborn (child) is placed in a child car seat, a back portion of the child car seat is inclined as much as possible so that the newborn can lie on its back in the seat, because the neck of the newborn is not strong yet. When a child weighing less than 10 kg is positioned in the seat, the child car seat is fixed backward with respect to a vehicle travelling direction (seat). When an impact load acts on the front part of a vehicle with the seat fixed in the way mentioned above, the newborn""s shoulder is subjected to a concentrated load through a shoulder belt.
FIG. 9 illustrates the magnitude of impact of a collision or the like acting on the newborn.
In FIG. 9, a seat belt S is applied to the newborn K who is laid at an angle of xcex1 with respect to a vertical line. Then, referring to impact force on the entire body of the newborn K caused by the collision or an emergency braking of the vehicle as F, the impact force on the shoulder of the newborn K as F1, and the impact force on the back of the newborn K as F2, the impact force F acting on the entire body of the newborn in the travelling direction of the vehicle is determined by a product of a mass of the newborn and deceleration. However, since the newborn K is braced in the child car seat, the impact force can be divided into a force component parallel to the back portion of the child car seat (namely the impact force F1 acting on the shoulder) and a force component perpendicular to the back portion of the child car seat (namely the impact force F2 acting on the back) as shown in formula (1).
F={square root over (F12+F22)}xe2x80x83xe2x80x83(1) 
And since an inclination angle of the child car seat is a, the following formulas (2), (3) are obtained.
F1=F sin xcex1xe2x80x83xe2x80x83(2) 
F2=F cos xcex1xe2x80x83xe2x80x83(3) 
With the newborn K laid in the child car seat in the most inclined position, when the angle xcex1increases, the force F1, acting on the shoulder becomes large in proportion to sin xcex1. Moreover, while the impact force F2 acting on the back is absorbed by the entire back portion, the impact force F1 acting on the shoulder is concentrated on a contact point between the seat belt and the shoulder. Therefore, the damage to the shoulder portion can be significant.
Since the conventional child car seat fixed backward to the vehicle""s travelling direction is so constructed that the impact force acts only on the shoulder belts at an impact time, the impact force concentrated on the frail shoulders of the newborn or child (hereafter referred to as xe2x80x9cchildxe2x80x9d)caused significant damage to the shoulder.
The object of the invention is to provide a child car seat in which an impact force acting on the shoulders of a child can be reduced by dispersing the impact force at the time of impact.
According to the present invention, a child car seat comprises a child car seat body, a back portion and a seat portion connected to the child car seat body. The back portion is rotatably connected to the child car seat body, and the back portion can be rotated between a normal position at a normal time where an angle between the back portion and a vertical plane is large, and an impact position at the impact time where the angle between the back portion and the vertical plane is small.
In the child car seat, the top end of the back portion may be rotatably connected to the child car seat body.
In the child car seat, the bottom end of the back portion may be connected to the seat portion through a spring member, and the back portion may take the normal position on the seat portion side at the normal time and the impact position away from the seat portion at the impact time.
In the child car seat, the bottom end of the back portion may be engaged by a hooking device connected to the child car seat body.
In the child car seat, the hooking device may have a hooking surface engaging the back portion in the normal position and a reset slope engaging with the back portion in the impact position.
In the child car seat, the hooking device may be connected to the child car seat body so that the device is allowed to swing freely.
In the child car seat, the hooking device may be biased by a spring toward the back portion.
In the child car seat, the bottom end of the back portion may be connected to the bottom by a connecting member to be broken at the time of impact. The back portion may take the normal position on the seat portion side at the normal time, and take the impact position where the connecting member is broken at the time of impact and the seat portion is away from the seat portion.
In the child car seat, a belt for holding the child may be installed between the bottom end of the back portion and the seat portion in order to rotate the back portion by force acting on the belt from the child at the impact time.
In the child car seat, the bottom end of the back portion may be rotatably connected to the child car seat body.
In the child car seat, the rear side of the back portion may be equipped with a moving wedge that moves along the back portion to rotate the back portion.
In the child car seat, the moving wedge may be arranged between the child car seat body and the back portion.
In the child car seat, the moving wedge may be arranged between an auxiliary plate installed on the child car seat body and the back portion.
In the child car seat, the moving wedge may be arranged between an auxiliary plate attached to the child car seat body and the back portion.
In the child car seat, the belt for holding the child may be installed between the moving wedge and the seat portion, and the moving wedge may be moved along the back portion by the force acting on the belt from the child to rotate the back portion.